Preparation: Put cream, butter and grated chocolate into a pan. The chocolate need not be grated fine. The cream can be replaced by skimming the top off raw milk poured into a wide basin and allowed to settle. Melt butter, chocolate, and cream in a double boiler, stirring to mix well. When melted, remove the double boiler from the fire, leaving the hot water in the bottom pan to keep it warm. Sift the powdered sugar in slowly, so that it will not form lumps, stirring constantly. Let stand 24 hr. in a cool place. (In winter, 12 hr. in a cold room will do.) At the end of this time, cut a piece of this chocolate about the size of a small nut, using a knife or spoon. Roll it into a ball in the palm of the hand until the outside of the bonbon begins to melt a little. Then roll it in grated or granulated chocolate, which will stick to it perfectly. Let stand 2 hr. before serving, but in a place that is not too cold, because these truffles are better when they are a little soft. Instead of rolling them into balls, you can also shape them to look more like truffles.